Issue #609: HOP, HOP, Astro-Hop!

 

Well, well, well, muchachos… November is almost here, and it looks as if we in Possum Swamp may have dodged a bullet hurricane-wise this season. The skies had been improving since the thunderstorms of summer diminished, and that had got me to thinking it might be time to do some visual deep sky observing in the ol’ backyard. Maybe even with my “big” telescope in these latter days, Zelda, a Zhumell (GSO) 10-inch Dobsonian.

Maybe. While clearer and drier as September came in, the sky could still be hazy, and there is considerable light pollution here at the suburban Chaos Manor South. Not horrible like downtown, no, but enough to make locating objects with a finder scope, much less a zero-power red-dot finder, a right good pain in the rear. I got to thinking I might want to put digital setting circles on Zelda.

If you’re a long-time fan of the Little Ol’ AstroBlog from Possum Swamp, you know I had DSCs on my long-gone truss tube Dob, Old Betsy. Sky Commanders they was, and they worked a treat. I think I saw more with Bets in the first year or two I had the ‘Commanders than I’d seen with her the previous decade. So, I started shopping. But it turned out ordering circles for the Dob wouldn't be so easy this time.

The problem, it appeared, would be mounting the encoders, the widgets that tell the DSC computer where the scope is pointed, to Zelda’s somewhat different altitude and azimuth axes. She is nicely equipped with smooth bearings and large tension knobs for altitude and a lazy-Susan-style azimuth bearing system, but those things make encoder mounting more complicated than with a simpler “Teflon on Ebony Star” Dobbie.

I did find a set of DSCs available with an encoder hardware kit for my GSO, but it was expensive, would have to be ordered from overseas, and it appeared I’d have to ship them one of the mount’s altitude trunnions for modification. All the way to Australia. That seemed like a deal-breaker to moi. I kept looking and found a digital circle vendor stateside who could provide encoders and encoder mountings for Z, but still…more than I was comfortable paying given—to be honest—the limited number of nights I observe with the Z-girl. If only there were another way…

Then, I ran across a YouTube video about that “another way.” It seemed there was a (free) program for smartphones, both iOS and Android smartphones, AstroHopper, that used a phone to replace digital setting circles. Unk was mighty skeptical, however.

Folks tried that years ago when smartphone astronomy apps that could find sky objects with the aid of a phone’s compass became popular. Oh, they worked well enough to point the way to naked eye objects but weren’t nearly accurate enough for use with a telescope. I didn’t imagine anything had changed, but I watched some more YouTube videos on AstroHopper anyhow.

Surprisingly, the consensus seemed to be AstroHopper does work with a telescope and delivers accuracy similar to DSCs.  I did note video posters seemed to have a range of results from “works great” to “well, sorta works.” Sounded to me like I should at least have a look-see at AstroHopper’s website, which I did:  AstroHopper - Web Application for Sky Navigation Manual.

What I found there sounded encouraging and convincing. Obviously, Artyom Beilis, the author, has been working on his app for a while and it seems rather mature. Yeah, it sounded good enough to make me want to at least give it a try:

AstroHopper (formerly known as SkyHopper) is a free and open-source web application developed by Artyom Beilis that helps to find objects across the night sky. It does this by allowing an accurate hop from a well-known and easily identifiable star to other fainter stars or DSO by measuring changes in pointing angles of the cell phone using built in gyroscope and gravity sensors. It is similar to Digital Setting Circles implemented in a smart phone.

Then came the hard part, figuring out how to mount the phone on the telescope’s tube. It needs to be secure and needs to be pointing along the scope’s optical axis. I had a couple of ideas how I might do that if ‘Hopper worked, but I certainly wasn’t going to go drillin’ holes in poor Zelda’s OTA without being convinced this was for real. The solution, then?

What came to mind was a smartphone camera mount for telescopes I’d bought some time back to take afocal Moon pictures for an S&T Test Report. Maybe I could use the phone-holder part of it to affix Siri to Zelda’s tube temporarily?  I taped the holder to Z with blue painters’ tape (to avoid damaging Zelda’s finish) using enough tape to ensure the iPhone would be held as securely as possible. I inserted my iPhone 14 Pro Max into the taped-down camera mount and called that “good enough.”

It looked wacky and Rube Goldberg-ish, and as a mild September evening came in, I didn’t have much hope. Hell, I felt a little silly, y’all. Nevertheless, I got Miss Z into the backyard, inserted a reasonably low power (50x), reasonably wide-field (70⁰) Bresser 25mm ocular into Zelda’s focuser, and got started.

I hadn’t installed the app on the phone yet. You don’t have to; you can just run it as a web page. Obviously, you have to have an internet connection, though, so if you plan to go to a dark site somewheres without a cell tower signal, you need to install AstroHopper on the phone (full instructions are on the ‘Hopper website). Anyhoo, with the web page up (it was in red-screen mode from the get-go), I set out to put it to the acid test.

When you have the app onscreen, you’ll get step by step instructions as to how to align AstroHopper, but in truth there ain’t much to it. Find a bright star near the object of your desire, center it in the eyepiece, tap “align” on the app, and touch the alignment star (or planet) on the displayed star chart.  Once ‘Hopper says it is aligned, enter your target's designation in a search box and you will be given onscreen directions—a line pointing the way and azimuth and altitude distance figures—to your object. Then, yep, just move the scope to the indicated spot and there you are. That’s what the app said, but, yeah, your skeptical old Uncle was skeptical.

Hokay, alignment star… I was after M13 as a first object, and while Herc was purty high on the September evening when I first gave AstroHopper a go, we were still experiencing some of the humidity and haze of summer, and I thought a brighter star than one of Hercules’ suns would be easier. Alkaid in Ursa Major, the end star of the dipper’s handle, was still well above the horizon. A bit far from the Great Globular, but, well, I was after an acid test. If (more like “when,” I thought) it didn’t work, I’d find a star closer to M13.

Alkaid in the center of the 25mm Bresser’s field (could have rounded up a crosshair eyepiece, but didn’t), I clicked “align,” and chose Alkaid on the map. StarHopper claimed it was aligned, so I typed M13 in the little box and followed the app’s directions to the Great Glob. When it indicated we was there, I put my eye to the eyepiece, expecting absolutely nothing…

Damn! There was M13! Not centered, no, but not on the field edge, either. Howsabout M92? Boom! M57? There was the little smoke ring. M56? Looked better than I thought it would. I was frankly amazed. I can only suppose cell phone compasses and accelerometers have improved a lot over the years. And obviously Mr. Beilis is a talented programmer.

Takeaways? Having an alignment star reasonably close to the target object helps, but it doesn’t have to be right next door. As with many alt-az DSC and goto systems, avoid alignment stars that are near zenith. Also, if you let your phone go to sleep, you will have to realign. It will claim to still be aligned, but it won’t be. Finally, yes, AstroHopper worked. It worked as well as many DSCs and better than some I’ve used. Only aligning on one star and using a compass and accelerometers rather than inherently more accurate encoders means it doesn’t yield the horizon-to-horizon alignment of the Sky Commanders, but for my purposes it is good enough.

Convinced AstroHopper at least worked, the next step for your old Uncle was ginning up some kind o’ more elegant mounting for the iPhone than fricking masking tape.  That was easy enough to do. The camera mount came with a knob-headed bolt that screws into the back of the phone-holder portion. I hated to take an electric drill to Zelda’s beautiful black steel tube, but if AstroHopper worked consistently, I judged doing surgery on the girl would be worth it as it might impel me to get Z under the stars more frequently.

I drilled an appropriate hole in Zeldas’s tube, and after I was done spent a little time cleaning up that hole with a file. Done, I inserted that knob-head bolt through the hole and fastened the phone-holder down. The result looked purty darned good, I must say. Now to see if my original success had been a fluke. Why not undertake “A Trio of Fall Globulars” from The Urban Astronomer’s Guide? The sky was clear, and all were riding high…

To cut to the chase? AstroHopper’s performance the first time out was not a fluke; it did every bit as well on this evening. Casually aligning on a star (no high-power crosshair eyepiece) again yielded good accuracy. I didn’t try to quantify it, but it appeared I could hit targets at least 20⁰ from alignment stars. Most objects were near the center of the field, some were centered, and none was “out.” I was happy with my phone mount, and had remembered to set “lock screen” to “never” so the iPhone didn’t go to sleep and ruin my alignment, so this run went considerably more smoothly than the first one.

So, me and Zelda hopped from globular to globular under (once again) humid and hazy October skies. How did those globs look in the 10-inch? That, muchachos, is a story for next time. While it seemed I’d only been out under the stars a few minutes, the falling dew and the wheeling vault of heaven that had sent old Hercules into the horizon told me Z and I had been voyaging the sky for hours, not minutes. I reluctantly covered the girl and headed inside for TV and Yell with the felines (well, catnip for them). Need I say it? It was a good night, y’all.

The Comet…

Of course, your lazy old Unk saw the comet, but being lazy, waited till Tsuchinshan-ATLAS had rounded the Sun and got into the evening sky before hunting her up. A good buddy of mine and a longtime friend of this here blog, astrophotographer Max Harrell, got some lovely pictures from our local dark site. Alas, the evening he and some other fellers headed out there was my teaching day (and night) at the University. So, I had to be content with the front yard of Chaos Manor South, which offers a view low enough in the west to allow me to spot the visitor.

And spot her visually was about all I did. I scanned around in the correct area with my much-loved Burgess 15x70 binoculars, and finally saw…well…a slightly fuzzy star. My SeeStar, Suzie, laughed at me and told me to go back in the house and have some Rebel Yell while she fetched the comet. Which she did in rather impressive fashion (above) given the sky quality and the comet’s low altitude.

Next Time:  A Trio of Fall Globulars with Zelda and Suzie…